Thermostat



July 13, 195 w. A. RAY ETAL THERMOSTAT Filed June 28, 1950 w m m ,m M m m 3 .H R: U A Xv MT L8 L5 WM; Y W

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Patented July 13, 1954 THERMOSTAT William A. Bay, North Hollywood, and Wilbert C.

Buescher, Alhambra, Calif., assignors to Gen- .eral Controls (30., Glendale, Calif., a corporation of California Application June 28, 1950, Serial No. 170,756

4 Claims. 1

The invention relates to electrical devices of the circuit-controlling type, and more particularly to bimetallic thermostats.

One object of the invention is to provide means for sealing the contacts of a thermostat or similar control device from dust or other foreign matter. This is of special importance in connection with a device wherein the interengagement of the contacts occurs gradually, as in a thermostat of the floating-contact type, as distinguished from one which employs snap-action to effect abrupt closing and opening of the contacts. As is brought out in the Ray Patent No. 2,274,938 issued March 3, 1942: in a thermostat of the floating-contact type the contact resistance, even across contacts having clean unoxidized faces, may have considerable influence on the operation of a circuit controlled by the contacts if the total resistance of the circuit is relatively low. It follows that any foreign matter between the contacts would further affect the contact resistance and cause erratic operation of such a circuit.

A more specific object is to provide a seal or dust-shield for the contacts which can be readily opened and reclosed for inspection of the contacts; this object being accomplished by means of a diaphragm, of material such as rubber, extending across, and elastically gripping, the open end of a cup-shaped contact-confining member.

As was mentioned hereinabove, the contact resistance of a thermostat of the floating-contact (non-snap-action) type may be a significant factor in the control of an electric circuit whose total resistance is relatively low; the contact resistance upon initial engagement of the contacts being so high that the voltage across the load device (such as a gas valve) is then insuflicient to effect its operation. With gradual increase of contact pressure the contact resistance is reduced until operation of the control device results. During the period while the contacts are interengaged but their effective resistance is high, the thermo-- stat, when it is of the usual bimetallic type, is very sensitive to ordinary sound waves which cause variation of the contact pressure and. resistance so that intermittent false operation of the control device may occur. It is another object of this invention to minimize the effect of sound waves on the thermostat; this object being accomplished (1) by providing an asymmetric slot in the bimetallic member so as to produce an unharmonious condition therein whereby microphonic action is dampened, or (2) by friction- 2 producing means acting on the free end of the bimetallic member.

For full understanding of the invention, and further appreciation of its objects and advantages, reference is to be had to the following detailed description and accompanying drawing, and to the appended claims.

In the drawing:

Figure 1 is a side view, mainly in section, of a bimetallic thermostat embodying the invention;

Figure 2 is a perspective view, to slightly reduced scale, of the bimetallic member or strip shown in Fig. 1 and Figure 3 is a side elevation of a modified form of bimetallic thermostat according to the invention.

In the drawing, the numeral ll indicates a support for the thermostat, which support may be of any suitable shape and size; the fragmentary portion of the support shown in the drawing including a hollow cylindrical boss I2 which is externally threaded for a nut I3. Generally indicated by the numeral M is a Ushaped bimetallic strip or member, shown per se in Fig. 2, having openings 15 and [5 adjacent the ends of its respective side arms ll and H3. The bimetallic member M is mounted by its side arm I! on the support (opening 15 fitting the boss l2) with a spacer [9 between it and the support. Between the side arms of the bimetallic member is a Ushaped arm 20, of resilient metal, having an opening at one of its ends fitting the supportboss [2; the arm 20, as well as the bimetallic member, being clamped to the support by nut l3.

Secured in the opening IS in arm 18 of the bimetallic member is a shouldered bushing 2| of thermoplastic insulating material; the outer end of the bushing having been headed-over by the application of heat and pressure. Pressed in the bore of bushing 22! is an electrical contact 22 which cooperates with another contact 23 mounted in an opening through the free end of the resilient arm 20. Secured, as by welding, to arm 20 is a cup-shaped member 24 having a central opening through which the tip of contact 23 protrudes. Covering the open end of cup-shaped member 24 is a diaphragm 25, of elastic insulating material such as rubber, having a beaded flange 26 which is snapped-over and tightly grips the flared rim of the cup. The diaphragm 25 has a central opening which fits a circumferential recess in bushing 21. A screw 21, threaded in an opening through the support and boss [2, is in engagement with the headed rear end of the normally-fixed contact 23 for adjusting the position mally-fixed contact 23 is electrically connected through arm 20, serving as the other connecting point for the thermostat.

The cup 24 and diaphragrir 2 i'*tog'etl'1errdrm--af dust-tight compartment for the cdntacts' fl 23. The diaphragm, because{ifitselasticity,"does 5 not appreciably impede normal movement of the bimetallic member in response ftO" temperature changes. The diaphragm can be readily opened and reclosed, for inspection of the contacts,'"by" stretching its flange 26 out of and into place on the rimof eup' zfi.

Referring now more particular-13'to 'Figf Zjth numeral? ir-"indi'ca-te's the sides of a slot critin the bimetallic member" 7 i fi an'dextendingfrom -"the cinolc'of its (Jthrough both side' arms of'the mom ber-"to the points-indicated. inFig; 1 by the broken lines 3 I. The slot 36 extends gnerallylengthwise of the side arms but asymmetricallywith respect to their-axes: Wehave' found=that-by slotting'a bimetallic strip obliquely; in the general manner P shownf an unharmoniouscon'dition 'is-produced in the'stri-pawhe'reby m-ic-iophoni'c-ac'tion of the same under the influence of sound waves isg'reat'ly-re-*" duced thedisadvantage-oi such "microphonic actiomun-dercertaimconditions of a thermostat} having been described in the statement of inven ti011':--

The thermostat sh'own in-Fig53 isthesameas" that of Fi-grl except for'the add itiori offrictiohal means for preventing vibration of the bimetalli'o" member; This' means' comprises a resilientblade' 36 s'ecurd'by-"a rivet3'l to the horizontalarm 'ofa right-angled bracket 3 5 which is mounted in place of the spacer"l9 of Fig: 1. The blade -36"bears'- against' the top' edg'e of'arm -18 bfthe bimetallic member; a screw 38; passing through ari opening' inthe'blade and" threaded in 'the* bracketybeing' provided for adjustirigthie'foriz of -'the"blad'e; A" small' amount-of" friction between" blade 36"an-'d** the bimetallic-amid is'effective t'o prevent-micro phonie-=actionof the arm without impeding its I normaltherrnosta'tic n'iovernent; In the' arra'rige-" member-Fig.8 -it-is not neces'sary to 51011 the bi m'e'tal u r The specifieembodiments of our inventiori-her- 55 inBhOW1'i"flI1ddeSCrib6d are susceptible of in'odifi cation-without departing fromthe' spirit of the invention, andwe intend' therefore to"be"limit'ed only byi the scope of the'appended claims:

We claim --as" our invention 1.-- In-an electrical "control" device? a support means-mounted omsa'idsuppdrt and movablein response -tQ-variations of a controllingcondition arr electrical contact carried" by said-- condition" responsivemeans "and"mo'vable therewith; a re-"" sil ient-arm mounted by oneof its'ends on said" supportg a normally-fixed-contact carried'by said arm and positioned forengagement by" said mov-" able-contact 'means mounted on said support for moving the-freeen'd of said arm-to effect 'adj-ust- Cir ' meritofeaid-normally-fixedcontact-toward and away from-said movable contact;-=andmeans forming a dust-tight compartment extending between, and-secured topsaid arm' and-said condi-- tion responsive means and *spacedlysurrounding both of said contacts, a portion of said compartmerit-forming means being of rubber-like elastic material adapted to flex in relative movement of the arm and the condition responsive means, the border of said portion having an elasticall gripping connection with the remainderof the compartnient iforrzfingmeans and bei'h'g *refadily removable tlfefefroirfi 2. In a thermostat: a support; a U-shaped bimetallic member mounted by one of its side arms Orr-said support; an electrical contact on the inside oi the free arm of said bimetallic member vabl'etherw'ith; a U-shaped resilient arm d on s idsii pport, the free end or" said arm en said movable contact; a normally fixe contacficarried by said free end of said'arm and-pdsitioned for engagement by said movable contact; means mounted on said support forinoving said free end of said arm to effect adjustment of said normally-fixed contact toward and away frofri'said inoyabi' and nfea'ns forminga dii'st ti'glit co "pa'it'nie'rit o s ism-m an relativem'ovrhent or tn'erfir and the" bimetallic member, the-"borderofsaid porftilin -having ari elastically"gripping 0o 56 with the" remainder of 'thecompartmen -fo1ming' means-arid bi'fi'greafii1y r'iiiovabl tlirefi d 3. In 3 an-' electrical cofit'ioYfdevioe? means mountcd-orrsaid 'supp'ort an In response to" variatio means fof i'nou gthe A K I justmrit of saidnoi' all'y fix contact-toward "'a U shaped'rsil nt f arm mounted on? said 'supp t',""thefreeeri'd of said-ai'm ex'tending 'ad aid in-stasis ori' j" tacti' a normally fixed co'n ac carried by said" free end of said arm 'fand"positior'ie d fore1"igage merit by saidino'vable seesaw" means'dniinted on gamsuppsrtro'r mature sa1d"fre'nd of sa "f arm to effect'adjustment of'said ncfinsuygjfiiaq contact'to w afdand awayf roin s aid movable contact; and means-forming -a dust tight compartv ment extending between, and secured 7to',-said' arm and saidbirritallic member and spacedly' surrounding both of said contacts-;saidcompartment forming 1 means comprising a rigid" cup:

shaped member secured to said arm and surrounding said normally-fixed contact, and a centrally-apertured flexible diaphragm, of rubberlike elastic material, covering the open end of the cup-shaped member and secured to said bimetallic member, said diaphragm having a flange portion elastically gripping the side wall of the cup-shaped member.

References Cited in the file of this patent UNITED STATES PATENTS Number Number 6 Name Date Boekel et a1. June 1, 1915 Valverde Jan. 8, 1935 Valverde Jan. 8, 1935 Johnson May 28, 1940 Ray Aug. 7, 1945 Miller et al. Sept. 10, 1946 Unger Apr. 15, 1947 Tramontini Nov. 22, 1949 

